I drove mine to Bristol and back today (348 mile round trip), and have managed 340 miles before getting down to quarter fill, and that is in spite of putting normal fuel in for the first time in over 6 months.... I drove really slowly all the way down there and didn't notice the fuel difference, but on the way home I made 'Relaxed progress' riding the boost in 5th as the traffic calming measures moved into the other lanes and found that it has lost the top end grunt and smoothness, so hopefully I can afford to start using it again next month (I obviously had to do a couple of full-out acceleration test runs as well for completeness)